Python 3.3 有什么新变化¶
本文介绍了 Python 3.3 相比 3.2 的新增特性。 Python 3.3 于 2012 年 9 月 29 日 发布。 有关完整详细信息,请参见 changelog。
参见
PEP 398 - Python 3.3 发布计划
摘要 -- 发布重点¶
新的语法特性:
新的库模块:
faulthandler
(帮助调试低层级的崩溃)ipaddress
(代表 IP 地址和掩码的高层级对象)lzma
(使用 XZ / LZMA 算法压缩数据)unittest.mock
(使用模拟对象替换你的受测试系统中的某些部分)
新的内置特性:
重写 I/O 异常的层次结构.
实现的改进:
基于
importlib
重写 import machinery更紧凑的 Unicode 字符串。
更紧凑的 属性字典。
显著改进的库模块:
安全改进:
哈希随机化被默认启用。
请继续阅读有关面向用户的改变的详细清单。
PEP 405: 虚拟环境¶
虚拟环境有助于创建 独立的 Python 设置,同时共享全系统的基础安装,便于维护。 虚拟环境有自己的私有站点包(即本地安装的库),并可选择与系统范围的站点包分离。 虚拟环境的概念和实现 受到流行的``virtualenv`` 第三方 包 的启发,但受益于与解释器 核心更紧密的集成。
本 PEP 添加了 venv
模块用于编程访问,以及 pyvenv
脚本用于命令在线访问和管理。 Python 解释器会检查 pyvenv.cfg
,文件的存在标志着虚拟环境目录树的基础。
参见
- PEP 405 - Python虚拟环境
PEP 由 Carl Meyer 撰写 ; 由 Carl Meyer 和 Vinay Sajip 实现。
PEP 420: 隐式命名空间包¶
原生支持不要求 __init__.py
标记文件和可以自动跨越多个路径节的包目录(灵感来自多个命名空间包的第三方方案,如 PEP 420 中所述)
参见
- PEP 420 - 隐式命名空间包
PEP 由 Eric V. Smith 撰写,由 Eric V. Smith 和 Barry Warsaw 实现
PEP 3118: 新的内存视图实现和缓冲协议文档¶
PEP 3118 的实现已获得大幅改进。
新的 memoryview 实现全面修复了 Py_buffer 结构体中曾导致多起崩溃报告的动态分配字段的所有权和生命周期问题。 此外,还修复了多个函数在非连续或多维输入时崩溃或返回不正确结果的问题。
现在 memoryview 对象具有符合 PEP-3118 标准的 getbufferproc(),可以检查使用者的请求类型。 新增了许多新的特性,其中的大部分已适用于非连续数组和带有子偏移量的数组。
文档已进行更新,清楚地列出了导出方和使用方的责任。 缓冲区请求旗标志被划分为基本旗标和复合旗标。 对非连续和多维的 NumPy 风格数组的内存布局进行了说明。
相关特性¶
现在 struct 模块语法中所有原生单字符格式指示符(可以选择添加 '@' 前缀)均受到支持。
在某些限制条件下,cast() 方法允许改变 C 连续数组的格式和形状。
任何数组类型都支持多维列表的表示形式。
任何数组类型都支持多维比较操作。
格式为 B、b 或 c 的可哈希(只读)类型的一维 memoryview 现在将是可哈希的。 (由 Antoine Pitrou 在 bpo-13411 中贡献。)
支持对 1 维数据类型的任意切片。 例如,现在可以通过使用负步长值以 O(1) 复杂度对 memoryview 进行翻转。
API 的变化¶
官方的最大维度数量限制已更改为 64。
空形状、区间和子偏移量的表示形式现在是空元组而不是
None
。现在对格式为 'B' (无符号字节型) 的 memoryview 元素的访问将返回一个整数(遵循结构体模块语法)。 要返回字节串对象则必须先将视图强制转换为 'c'。
现在 memoryview 比较将使用操作数的逻辑结构并会按值来比较所有数组元素。 结构体模块语法中的所有格式化字符串均受到支持。 带有不可识别的格式化字符串的视图仍然被允许,但无论视图内容如何比较结果总是不相等。
更多改变请参阅 Build and C API Changes 和 Porting C code。
(由 Stefan Krah 在 bpo-10181 中贡献。)
参见
PEP 3118 - 修改缓冲区协议
PEP 393: 灵活的字符串表示¶
Unicode字符串类型已改为支持多种内部表示法,具体取决于所表示的字符串中具有最大 Unicode 序号(1、2 或 4 字节)的字符 。 这样,在常见情况下可以节省空间,但在所有系统上都能使用完整的 UCS-4。 对于使用现有应用程序接口的兼容性 来说,可能会并行存在几种表示法;随着时间的推移,这种兼容性 应逐步淘汰。
在 Python 一方,此项改变应当没有任何缺点。
在 C API 方面,PEP 393 完全向下兼容。 旧的 API 至少还能使用五年。 使用传统 API 的应用程序不会完全受益于内存的减少,或者更糟的是,可能会使用更多的内存,因为 Python 可能需要维护每个字符串的两个版本(传统格式和新的高效存储)。
功能¶
由 PEP 393 引入的改变如下:
Python 现在始终支持全部 Unicode 码位,包括非 BMP 码位 (即从``U+0000`` 到
U+10FFFF
)。 窄编译版本和宽编译版本之间的区别已不复存在,Python 现在的行为就像宽编译版本,甚至在 Windows 下也是如此。随着窄编译版本的消亡,窄编译版本特有的问题也得到了解决,例如:
现在
len()
对于非 BMP 字符总是返回 1,因此len('\U0010FFFF') == 1
;替换对不会在字符串字面值中重新合并,因此
'\uDBFF\uDFFF' != '\U0010FFFF'
;索引或切分非 BMP 字符会返回预期的值,因此
'\U0010FFFF'[0]
现在会返回'\U0010FFFF'
而不是'\uDBFF'
;标准库中的所有其他函数现在都能正确处理非 BMP 代码点。
sys.maxunicode
的值现在总是1114111
(十六进制为0x10FFFF
)。PyUnicode_GetMax()
函数仍返回0xFFFF
或0x10FFFF
以便向下兼容,但不应与新的 Unicode API 一起使用 (参见 bpo-13054)。./configure
标志--with-wide-unicode
已被移除。
性能和资源使用情况¶
现在,Unicode 字符串的存储取决于字符串中的最高码位:
纯 ASCII 和 Latin1 字符串 (
U+0000-U+00FF
) 每个码位使用 1 个字节;BMP 字符串 (
U+0000-U+FFFF
) 每个码位使用 2 个字节;非 BMP 字符串 (
U+10000-U+10FFFF
) 每个码位使用 4 个字节。
这样做的效果是,对于大多数应用而言,字符串存储的内存使用量应该会大幅减少 —— 尤其是与以前的宽 unicode 版本相比 —— 因为在许多情况下,即使在国际环境中,字符串也将是纯 ASCII 格式(因为许多字符串存储的是非人类语言数据,如 XML 片段、HTTP 标头、JSON 编码数据等)。 出于同样的原因,我们还希望它能提高非小应用程序的 CPU 缓存效率。 在 Django 基准测试中,Python 3.3 的内存使用量比 Python 3.2 少两到三倍,比 Python 2.7 略好一些(详情请参见 PEP)。
参见
- PEP 393 - 灵活的字符串表示
PEP 由 Martin von Löwis 撰写 ; 由 Torsten Becker 和 Martin von Löwis 实现。
PEP 397: 适用于Windows的Python启动器¶
Python 3.3 的 Windows 安装程序现在包含一个 py
启动程序,可用于以版本无关的方式启动 Python 应用程序。
双击 *.py
文件时会隐式调用该启动器。 如果系统中只安装了一个 Python 版本,则将使用该版本运行文件。 如果安装了多个版本,则默认使用最新版本,但也可以通过在 Python 脚本中加入 Unix 风格的“shebang 行”来覆盖该版本。
启动器也可以作为 py
应用程序在命令行中显式使用。运行 py
遵循与隐式启动脚本相同的版本选择规则,但可以通过传递适当的参数来选择更具体的版本(例如,当 Python 2 也已安装时,使用 -3
来请求 Python 3;当安装了较新的 Python 版本时,使用 -2.6
来特别请求较早的 Python 版本)。
除了启动器之外,Windows 安装程序现在还包含一个选项,可将新安装的 Python 添加到系统 PATH 中。 (由 Brian Curtin 在 bpo-3561 中贡献)。
参见
- PEP 397 - 适用于Windows的Python启动器
PEP 由 Mark Hammond 和 Martin v. Löwis 撰写 ; 由 Vinay Sajip实现。
启动器文档: 适用于Windows的Python启动器
安装器 PATH 修改: 查找Python可执行文件
PEP 3151: 重写 OS 和 IO 异常的层次结构¶
现在,由操作系统错误引发的异常层次结构既得到了简化,又更加精细。
您不必再为在 OSError
、IOError
、EnvironmentError
、WindowsError
、mmap.error
、socket.error
或 select.error
之间选择合适的异常类型而烦恼。 所有这些异常类型现在都只有一个: OSError
。 出于兼容性考虑,其他名称将作为别名保留。
此外,现在捕捉特定错误条件也更容易了。无需从 errno
模块中检查 errno
属性(或 args[0]
)中的特定常量,您可以捕捉适当的 OSError
子类。可用的子类如下:
并且 ConnectionError
本身具有细粒度的子类:
有了新的异常,现在就可以避免 errno
的常见用法了。 例如,下面是为 Python 3.2 编写的代码:
from errno import ENOENT, EACCES, EPERM
try:
with open("document.txt") as f:
content = f.read()
except IOError as err:
if err.errno == ENOENT:
print("document.txt file is missing")
elif err.errno in (EACCES, EPERM):
print("You are not allowed to read document.txt")
else:
raise
现在无需导入 errno
,也无需手动检查异常属性:
try:
with open("document.txt") as f:
content = f.read()
except FileNotFoundError:
print("document.txt file is missing")
except PermissionError:
print("You are not allowed to read document.txt")
参见
- PEP 3151 - 重写 OS 和 IO 异常的层次结构
PEP 由 Antoine Pitrou 撰写并实现
PEP 380: 委托给子生成器的语法¶
PEP 380 增加了 yield from
表达式,允许 generator 将其部分操作委托给另一个生成器。 这样,包含 yield
的代码部分就可以被分解出来,放在另一个生成器中。 此外,还允许子生成器返回一个值,并将该值提供给委托生成器。
虽然 yield from
表达式主要用于委托给子生成器,但它实际上允许委托给任意子生成器。
对于简单的迭代器而言,yield from iterable
本质上只是 for item in iterable: yield item
的简写形式:
>>> def g(x):
... yield from range(x, 0, -1)
... yield from range(x)
...
>>> list(g(5))
[5, 4, 3, 2, 1, 0, 1, 2, 3, 4]
However, unlike an ordinary loop, yield from
allows subgenerators to
receive sent and thrown values directly from the calling scope, and
return a final value to the outer generator:
>>> def accumulate():
... tally = 0
... while 1:
... next = yield
... if next is None:
... return tally
... tally += next
...
>>> def gather_tallies(tallies):
... while 1:
... tally = yield from accumulate()
... tallies.append(tally)
...
>>> tallies = []
>>> acc = gather_tallies(tallies)
>>> next(acc) # Ensure the accumulator is ready to accept values
>>> for i in range(4):
... acc.send(i)
...
>>> acc.send(None) # Finish the first tally
>>> for i in range(5):
... acc.send(i)
...
>>> acc.send(None) # Finish the second tally
>>> tallies
[6, 10]
The main principle driving this change is to allow even generators that are
designed to be used with the send
and throw
methods to be split into
multiple subgenerators as easily as a single large function can be split into
multiple subfunctions.
参见
- PEP 380 - 委托给子生成器的语法
PEP 由 Greg Ewing 撰写,由 Greg Ewing 实现。由 Renaud Blanch,Ryan Kelly 和 Nick Coghlan 集成到3.3,由 Zbigniew Jędrzejewski-Szmek 和 Nick Coghlan 编写文档
PEP 409: 清除异常上下文¶
PEP 409 introduces new syntax that allows the display of the chained exception context to be disabled. This allows cleaner error messages in applications that convert between exception types:
>>> class D:
... def __init__(self, extra):
... self._extra_attributes = extra
... def __getattr__(self, attr):
... try:
... return self._extra_attributes[attr]
... except KeyError:
... raise AttributeError(attr) from None
...
>>> D({}).x
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 8, in __getattr__
AttributeError: x
Without the from None
suffix to suppress the cause, the original
exception would be displayed by default:
>>> class C:
... def __init__(self, extra):
... self._extra_attributes = extra
... def __getattr__(self, attr):
... try:
... return self._extra_attributes[attr]
... except KeyError:
... raise AttributeError(attr)
...
>>> C({}).x
Traceback (most recent call last):
File "<stdin>", line 6, in __getattr__
KeyError: 'x'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 8, in __getattr__
AttributeError: x
No debugging capability is lost, as the original exception context remains available if needed (for example, if an intervening library has incorrectly suppressed valuable underlying details):
>>> try:
... D({}).x
... except AttributeError as exc:
... print(repr(exc.__context__))
...
KeyError('x',)
参见
- PEP 409 - 清除异常上下文
PEP 由 Ethan Furman 撰写 ,由 Ethan Furman 和 Nick Coghlan 实现。
PEP 414: 显式的Unicode文本¶
To ease the transition from Python 2 for Unicode aware Python applications
that make heavy use of Unicode literals, Python 3.3 once again supports the
"u
" prefix for string literals. This prefix has no semantic significance
in Python 3, it is provided solely to reduce the number of purely mechanical
changes in migrating to Python 3, making it easier for developers to focus on
the more significant semantic changes (such as the stricter default
separation of binary and text data).
参见
- PEP 414 - 显式的Unicode文本
PEP 由 Armin Ronacher 撰写
PEP 3155: 类和函数的限定名称¶
Functions and class objects have a new __qualname__
attribute representing
the "path" from the module top-level to their definition. For global functions
and classes, this is the same as __name__
.
For other functions and classes,
it provides better information about where they were actually defined, and
how they might be accessible from the global scope.
Example with (non-bound) methods:
>>> class C:
... def meth(self):
... pass
...
>>> C.meth.__name__
'meth'
>>> C.meth.__qualname__
'C.meth'
Example with nested classes:
>>> class C:
... class D:
... def meth(self):
... pass
...
>>> C.D.__name__
'D'
>>> C.D.__qualname__
'C.D'
>>> C.D.meth.__name__
'meth'
>>> C.D.meth.__qualname__
'C.D.meth'
Example with nested functions:
>>> def outer():
... def inner():
... pass
... return inner
...
>>> outer().__name__
'inner'
>>> outer().__qualname__
'outer.<locals>.inner'
The string representation of those objects is also changed to include the new, more precise information:
>>> str(C.D)
"<class '__main__.C.D'>"
>>> str(C.D.meth)
'<function C.D.meth at 0x7f46b9fe31e0>'
参见
- PEP 3155 - 类和函数的限定名称
PEP 由 Antoine Pitrou 撰写并实现
PEP 412: Key-Sharing Dictionary¶
Dictionaries used for the storage of objects' attributes are now able to share part of their internal storage between each other (namely, the part which stores the keys and their respective hashes). This reduces the memory consumption of programs creating many instances of non-builtin types.
参见
- PEP 412 - Key-Sharing Dictionary
PEP 由 Mark Shannon 撰写并实现。
PEP 362: 函数签名对象¶
A new function inspect.signature()
makes introspection of python
callables easy and straightforward. A broad range of callables is supported:
python functions, decorated or not, classes, and functools.partial()
objects. New classes inspect.Signature
, inspect.Parameter
and inspect.BoundArguments
hold information about the call signatures,
such as, annotations, default values, parameters kinds, and bound arguments,
which considerably simplifies writing decorators and any code that validates
or amends calling signatures or arguments.
参见
- PEP 362: - 函数签名对象
PEP 由 Brett Cannon,Yury Selivanov,Larry Hastings,Jiwon Seo 撰写,由 Yury Selivanov 实现
PEP 421: 添加 sys.implementation¶
A new attribute on the sys
module exposes details specific to the
implementation of the currently running interpreter. The initial set of
attributes on sys.implementation
are name
, version
,
hexversion
, and cache_tag
.
The intention of sys.implementation
is to consolidate into one namespace
the implementation-specific data used by the standard library. This allows
different Python implementations to share a single standard library code base
much more easily. In its initial state, sys.implementation
holds only a
small portion of the implementation-specific data. Over time that ratio will
shift in order to make the standard library more portable.
One example of improved standard library portability is cache_tag
. As of
Python 3.3, sys.implementation.cache_tag
is used by importlib
to
support PEP 3147 compliance. Any Python implementation that uses
importlib
for its built-in import system may use cache_tag
to control
the caching behavior for modules.
SimpleNamespace¶
The implementation of sys.implementation
also introduces a new type to
Python: types.SimpleNamespace
. In contrast to a mapping-based
namespace, like dict
, SimpleNamespace
is attribute-based, like
object
. However, unlike object
, SimpleNamespace
instances
are writable. This means that you can add, remove, and modify the namespace
through normal attribute access.
参见
- PEP 421 - 添加 sys.implementation
PEP 由 Eric Snow 撰写并实现
使用 importlib 作为导入的实现¶
bpo-2377 - Replace __import__ w/ importlib.__import__
bpo-13959 - Re-implement parts of imp
in pure Python
bpo-14605 - Make import machinery explicit
bpo-14646 - Require loaders set __loader__ and __package__
The __import__()
function is now powered by importlib.__import__()
.
This work leads to the completion of "phase 2" of PEP 302. There are
multiple benefits to this change. First, it has allowed for more of the
machinery powering import to be exposed instead of being implicit and hidden
within the C code. It also provides a single implementation for all Python VMs
supporting Python 3.3 to use, helping to end any VM-specific deviations in
import semantics. And finally it eases the maintenance of import, allowing for
future growth to occur.
For the common user, there should be no visible change in semantics. For those whose code currently manipulates import or calls import programmatically, the code changes that might possibly be required are covered in the Porting Python code section of this document.
新的API¶
One of the large benefits of this work is the exposure of what goes into
making the import statement work. That means the various importers that were
once implicit are now fully exposed as part of the importlib
package.
The abstract base classes defined in importlib.abc
have been expanded
to properly delineate between meta path finders
and path entry finders by introducing
importlib.abc.MetaPathFinder
and
importlib.abc.PathEntryFinder
, respectively. The old ABC of
importlib.abc.Finder
is now only provided for backwards-compatibility
and does not enforce any method requirements.
In terms of finders, importlib.machinery.FileFinder
exposes the
mechanism used to search for source and bytecode files of a module. Previously
this class was an implicit member of sys.path_hooks
.
For loaders, the new abstract base class importlib.abc.FileLoader
helps
write a loader that uses the file system as the storage mechanism for a module's
code. The loader for source files
(importlib.machinery.SourceFileLoader
), sourceless bytecode files
(importlib.machinery.SourcelessFileLoader
), and extension modules
(importlib.machinery.ExtensionFileLoader
) are now available for
direct use.
ImportError
now has name
and path
attributes which are set when
there is relevant data to provide. The message for failed imports will also
provide the full name of the module now instead of just the tail end of the
module's name.
The importlib.invalidate_caches()
function will now call the method with
the same name on all finders cached in sys.path_importer_cache
to help
clean up any stored state as necessary.
可见的改变¶
For potential required changes to code, see the Porting Python code section.
Beyond the expanse of what importlib
now exposes, there are other
visible changes to import. The biggest is that sys.meta_path
and
sys.path_hooks
now store all of the meta path finders and path entry
hooks used by import. Previously the finders were implicit and hidden within
the C code of import instead of being directly exposed. This means that one can
now easily remove or change the order of the various finders to fit one's needs.
Another change is that all modules have a __loader__
attribute, storing the
loader used to create the module. PEP 302 has been updated to make this
attribute mandatory for loaders to implement, so in the future once 3rd-party
loaders have been updated people will be able to rely on the existence of the
attribute. Until such time, though, import is setting the module post-load.
Loaders are also now expected to set the __package__
attribute from
PEP 366. Once again, import itself is already setting this on all loaders
from importlib
and import itself is setting the attribute post-load.
None
is now inserted into sys.path_importer_cache
when no finder
can be found on sys.path_hooks
. Since imp.NullImporter
is not
directly exposed on sys.path_hooks
it could no longer be relied upon to
always be available to use as a value representing no finder found.
All other changes relate to semantic changes which should be taken into consideration when updating code for Python 3.3, and thus should be read about in the Porting Python code section of this document.
(由 Brett Cannon 编写的实现)
其他语言特性修改¶
对Python 语言核心进行的小改动:
Added support for Unicode name aliases and named sequences. Both
unicodedata.lookup()
and'\N{...}'
now resolve name aliases, andunicodedata.lookup()
resolves named sequences too.(由 Ezio Melotti 在 bpo-12753 中贡献。)
Unicode 数据库更新至 UCD 版本 6.1.0
Equality comparisons on
range()
objects now return a result reflecting the equality of the underlying sequences generated by those range objects. (bpo-13201)The
count()
,find()
,rfind()
,index()
andrindex()
methods ofbytes
andbytearray
objects now accept an integer between 0 and 255 as their first argument.(由 Petri Lehtinen 在 bpo-12170 中贡献。)
The
rjust()
,ljust()
, andcenter()
methods ofbytes
andbytearray
now accept abytearray
for thefill
argument. (Contributed by Petri Lehtinen in bpo-12380.)New methods have been added to
list
andbytearray
:copy()
andclear()
(bpo-10516). Consequently,MutableSequence
now also defines aclear()
method (bpo-11388).Raw bytes literals can now be written
rb"..."
as well asbr"..."
.(由 Antoine Pitrou 在 bpo-13748 中贡献。)
dict.setdefault()
now does only one lookup for the given key, making it atomic when used with built-in types.(由 Filip Gruszczyński 在 bpo-13521 中贡献。)
The error messages produced when a function call does not match the function signature have been significantly improved.
(由 Benjamin Peterson 贡献。)
A Finer-Grained Import Lock¶
Previous versions of CPython have always relied on a global import lock.
This led to unexpected annoyances, such as deadlocks when importing a module
would trigger code execution in a different thread as a side-effect.
Clumsy workarounds were sometimes employed, such as the
PyImport_ImportModuleNoBlock()
C API function.
In Python 3.3, importing a module takes a per-module lock. This correctly serializes importation of a given module from multiple threads (preventing the exposure of incompletely initialized modules), while eliminating the aforementioned annoyances.
(由 Antoine Pitrou 在 bpo-9260 中贡献。)
Builtin functions and types¶
open()
gets a new opener parameter: the underlying file descriptor for the file object is then obtained by calling opener with (file, flags). It can be used to use custom flags likeos.O_CLOEXEC
for example. The'x'
mode was added: open for exclusive creation, failing if the file already exists.print()
: added the flush keyword argument. If the flush keyword argument is true, the stream is forcibly flushed.hash()
: hash randomization is enabled by default, seeobject.__hash__()
andPYTHONHASHSEED
.The
str
type gets a newcasefold()
method: return a casefolded copy of the string, casefolded strings may be used for caseless matching. For example,'ß'.casefold()
returns'ss'
.The sequence documentation has been substantially rewritten to better explain the binary/text sequence distinction and to provide specific documentation sections for the individual builtin sequence types (bpo-4966).
新增模块¶
faulthandler¶
This new debug module faulthandler
contains functions to dump Python tracebacks explicitly,
on a fault (a crash like a segmentation fault), after a timeout, or on a user
signal. Call faulthandler.enable()
to install fault handlers for the
SIGSEGV
, SIGFPE
, SIGABRT
, SIGBUS
, and
SIGILL
signals. You can also enable them at startup by setting the
PYTHONFAULTHANDLER
environment variable or by using -X
faulthandler
command line option.
Linux 上的段错误示例:
$ python -q -X faulthandler
>>> import ctypes
>>> ctypes.string_at(0)
Fatal Python error: Segmentation fault
Current thread 0x00007fb899f39700:
File "/home/python/cpython/Lib/ctypes/__init__.py", line 486 in string_at
File "<stdin>", line 1 in <module>
Segmentation fault
ipaddress¶
The new ipaddress
module provides tools for creating and manipulating
objects representing IPv4 and IPv6 addresses, networks and interfaces (i.e.
an IP address associated with a specific IP subnet).
(由 Google 和 Peter Moody 在 bpo-3144 中贡献。)
lzma¶
The newly added lzma
module provides data compression and decompression
using the LZMA algorithm, including support for the .xz
and .lzma
file formats.
(由 Nadeem Vawda 和 Per Øyvind Karlsen 在 bpo-6715 中贡献。)
改进的模块¶
abc¶
Improved support for abstract base classes containing descriptors composed with
abstract methods. The recommended approach to declaring abstract descriptors is
now to provide __isabstractmethod__
as a dynamically updated
property. The built-in descriptors have been updated accordingly.
abc.abstractproperty
has been deprecated, useproperty
withabc.abstractmethod()
instead.abc.abstractclassmethod
has been deprecated, useclassmethod
withabc.abstractmethod()
instead.abc.abstractstaticmethod
has been deprecated, usestaticmethod
withabc.abstractmethod()
instead.
(由 Pablo Galindo 在 bpo-11610 中贡献。)
abc.ABCMeta.register()
now returns the registered subclass, which means
it can now be used as a class decorator (bpo-10868).
array¶
The array
module supports the long long type using q
and
Q
type codes.
(由 Oren Tirosh 和 Hirokazu Yamamoto 在 bpo-1172711 中贡献。)
base64¶
ASCII-only Unicode strings are now accepted by the decoding functions of the
base64
modern interface. For example, base64.b64decode('YWJj')
returns b'abc'
. (Contributed by Catalin Iacob in bpo-13641.)
binascii¶
In addition to the binary objects they normally accept, the a2b_
functions
now all also accept ASCII-only strings as input. (Contributed by Antoine
Pitrou in bpo-13637.)
bz2¶
bz2
模块已被重新编写。 在此过程中,添加了一些新的特征:
新的
bz2.open()
函数:以二进制或文本模式打开 bzip2 压缩文件。bz2.BZ2File
现在可以读写任意文件型对象,具体方式是通过其构造器的 fileobj 参数。(由 Nadeem Vawda 在 bpo-5863 中贡献。)
bz2.BZ2File
andbz2.decompress()
can now decompress multi-stream inputs (such as those produced by the pbzip2 tool).bz2.BZ2File
can now also be used to create this type of file, using the'a'
(append) mode.(由 Nir Aides 在 bpo-1625 中贡献。)
bz2.BZ2File
now implements all of theio.BufferedIOBase
API, except for thedetach()
andtruncate()
methods.
编码器¶
The mbcs
codec has been rewritten to handle correctly
replace
and ignore
error handlers on all Windows versions. The
mbcs
codec now supports all error handlers, instead of only
replace
to encode and ignore
to decode.
A new Windows-only codec has been added: cp65001
(bpo-13216). It is the
Windows code page 65001 (Windows UTF-8, CP_UTF8
). For example, it is used
by sys.stdout
if the console output code page is set to cp65001 (e.g., using
chcp 65001
command).
Multibyte CJK decoders now resynchronize faster. They only ignore the first
byte of an invalid byte sequence. For example, b'\xff\n'.decode('gb2312',
'replace')
now returns a \n
after the replacement character.
Incremental CJK codec encoders are no longer reset at each call to their encode() methods. For example:
>>> import codecs
>>> encoder = codecs.getincrementalencoder('hz')('strict')
>>> b''.join(encoder.encode(x) for x in '\u52ff\u65bd\u65bc\u4eba\u3002 Bye.')
b'~{NpJ)l6HK!#~} Bye.'
This example gives b'~{Np~}~{J)~}~{l6~}~{HK~}~{!#~} Bye.'
with older Python
versions.
unicode_internal
编解码器已被弃用。
collections¶
Addition of a new ChainMap
class to allow treating a
number of mappings as a single unit. (Written by Raymond Hettinger for
bpo-11089, made public in bpo-11297.)
The abstract base classes have been moved in a new collections.abc
module, to better differentiate between the abstract and the concrete
collections classes. Aliases for ABCs are still present in the
collections
module to preserve existing imports. (bpo-11085)
The Counter
class now supports the unary +
and -
operators, as well as the in-place operators +=
, -=
, |=
, and
&=
. (Contributed by Raymond Hettinger in bpo-13121.)
contextlib¶
ExitStack
now provides a solid foundation for
programmatic manipulation of context managers and similar cleanup
functionality. Unlike the previous contextlib.nested
API (which was
deprecated and removed), the new API is designed to work correctly
regardless of whether context managers acquire their resources in
their __init__
method (for example, file objects) or in their
__enter__
method (for example, synchronisation objects from the
threading
module).
crypt¶
Addition of salt and modular crypt format (hashing method) and the mksalt()
function to the crypt
module.
curses¶
If the
curses
module is linked to the ncursesw library, use Unicode functions when Unicode strings or characters are passed (e.g.waddwstr()
), and bytes functions otherwise (e.g.waddstr()
).Use the locale encoding instead of
utf-8
to encode Unicode strings.curses.window
添加了新的curses.window.encoding
属性。curses.window
类有一个新的get_wch()
方法用来获取一个宽字符。curses
模块有一个新的unget_wch()
函数用来推入一个宽字符以便下一个get_wch()
将返回它。
(由 Iñigo Serna 在 bpo-6755 中贡献。)
datetime¶
Equality comparisons between naive and aware
datetime
instances now returnFalse
instead of raisingTypeError
(bpo-15006).New
datetime.datetime.timestamp()
method: Return POSIX timestamp corresponding to thedatetime
instance.The
datetime.datetime.strftime()
method supports formatting years older than 1000.The
datetime.datetime.astimezone()
method can now be called without arguments to convert datetime instance to the system timezone.
decimal¶
- bpo-7652 - integrate fast native decimal arithmetic.
C-module and libmpdec written by Stefan Krah.
The new C version of the decimal module integrates the high speed libmpdec library for arbitrary precision correctly rounded decimal floating-point arithmetic. libmpdec conforms to IBM's General Decimal Arithmetic Specification.
Performance gains range from 10x for database applications to 100x for numerically intensive applications. These numbers are expected gains for standard precisions used in decimal floating-point arithmetic. Since the precision is user configurable, the exact figures may vary. For example, in integer bignum arithmetic the differences can be significantly higher.
The following table is meant as an illustration. Benchmarks are available at https://www.bytereef.org/mpdecimal/quickstart.html.
decimal.py
_decimal
加速
pi
42.02秒
0.345秒
120倍
telco
172.19秒
5.68秒
30倍
psycopg
3.57秒
0.29秒
12倍
相关特性¶
The
FloatOperation
signal optionally enables stricter semantics for mixing floats and Decimals.If Python is compiled without threads, the C version automatically disables the expensive thread local context machinery. In this case, the variable
HAVE_THREADS
is set toFalse
.
API 的变化¶
C模块上下文限制(如下表),具体取决于计算机体系结构:
32位
64位
MAX_PREC
425000000
999999999999999999
MAX_EMAX
425000000
999999999999999999
MIN_EMIN
-425000000
-999999999999999999
In the context templates (
DefaultContext
,BasicContext
andExtendedContext
) the magnitude ofEmax
andEmin
has changed to999999
.The
Decimal
constructor in decimal.py does not observe the context limits and converts values with arbitrary exponents or precision exactly. Since the C version has internal limits, the following scheme is used: If possible, values are converted exactly, otherwiseInvalidOperation
is raised and the result is NaN. In the latter case it is always possible to usecreate_decimal()
in order to obtain a rounded or inexact value.The power function in decimal.py is always correctly rounded. In the C version, it is defined in terms of the correctly rounded
exp()
andln()
functions, but the final result is only "almost always correctly rounded".In the C version, the context dictionary containing the signals is a
MutableMapping
. For speed reasons,flags
andtraps
always refer to the sameMutableMapping
that the context was initialized with. If a new signal dictionary is assigned,flags
andtraps
are updated with the new values, but they do not reference the RHS dictionary.Pickling a
Context
produces a different output in order to have a common interchange format for the Python and C versions.The order of arguments in the
Context
constructor has been changed to match the order displayed byrepr()
.The
watchexp
parameter in thequantize()
method is deprecated.
email¶
Policy Framework¶
The email package now has a policy
framework. A
Policy
is an object with several methods and properties
that control how the email package behaves. The primary policy for Python 3.3
is the Compat32
policy, which provides backward
compatibility with the email package in Python 3.2. A policy
can be
specified when an email message is parsed by a parser
, or when a
Message
object is created, or when an email is
serialized using a generator
. Unless overridden, a policy passed
to a parser
is inherited by all the Message
object and sub-objects
created by the parser
. By default a generator
will use the policy of
the Message
object it is serializing. The default policy is
compat32
.
The minimum set of controls implemented by all policy
objects are:
max_line_length |
The maximum length, excluding the linesep character(s),
individual lines may have when a |
linesep |
The character used to separate individual lines when a
|
cte_type |
|
raise_on_defect |
导致一个 |
A new policy instance, with new settings, is created using the
clone()
method of policy objects. clone
takes
any of the above controls as keyword arguments. Any control not specified in
the call retains its default value. Thus you can create a policy that uses
\r\n
linesep characters like this:
mypolicy = compat32.clone(linesep='\r\n')
Policies can be used to make the generation of messages in the format needed by
your application simpler. Instead of having to remember to specify
linesep='\r\n'
in all the places you call a generator
, you can specify
it once, when you set the policy used by the parser
or the Message
,
whichever your program uses to create Message
objects. On the other hand,
if you need to generate messages in multiple forms, you can still specify the
parameters in the appropriate generator
call. Or you can have custom
policy instances for your different cases, and pass those in when you create
the generator
.
Provisional Policy with New Header API¶
While the policy framework is worthwhile all by itself, the main motivation for introducing it is to allow the creation of new policies that implement new features for the email package in a way that maintains backward compatibility for those who do not use the new policies. Because the new policies introduce a new API, we are releasing them in Python 3.3 as a provisional policy. Backwards incompatible changes (up to and including removal of the code) may occur if deemed necessary by the core developers.
The new policies are instances of EmailPolicy
,
and add the following additional controls:
refold_source |
Controls whether or not headers parsed by a
|
header_factory |
A callable that take a |
The header_factory
is the key to the new features provided by the new
policies. When one of the new policies is used, any header retrieved from
a Message
object is an object produced by the header_factory
, and any
time you set a header on a Message
it becomes an object produced by
header_factory
. All such header objects have a name
attribute equal
to the header name. Address and Date headers have additional attributes
that give you access to the parsed data of the header. This means you can now
do things like this:
>>> m = Message(policy=SMTP)
>>> m['To'] = 'Éric <foo@example.com>'
>>> m['to']
'Éric <foo@example.com>'
>>> m['to'].addresses
(Address(display_name='Éric', username='foo', domain='example.com'),)
>>> m['to'].addresses[0].username
'foo'
>>> m['to'].addresses[0].display_name
'Éric'
>>> m['Date'] = email.utils.localtime()
>>> m['Date'].datetime
datetime.datetime(2012, 5, 25, 21, 39, 24, 465484, tzinfo=datetime.timezone(datetime.timedelta(-1, 72000), 'EDT'))
>>> m['Date']
'Fri, 25 May 2012 21:44:27 -0400'
>>> print(m)
To: =?utf-8?q?=C3=89ric?= <foo@example.com>
Date: Fri, 25 May 2012 21:44:27 -0400
You will note that the unicode display name is automatically encoded as
utf-8
when the message is serialized, but that when the header is accessed
directly, you get the unicode version. This eliminates any need to deal with
the email.header
decode_header()
or
make_header()
functions.
You can also create addresses from parts:
>>> m['cc'] = [Group('pals', [Address('Bob', 'bob', 'example.com'),
... Address('Sally', 'sally', 'example.com')]),
... Address('Bonzo', addr_spec='bonz@laugh.com')]
>>> print(m)
To: =?utf-8?q?=C3=89ric?= <foo@example.com>
Date: Fri, 25 May 2012 21:44:27 -0400
cc: pals: Bob <bob@example.com>, Sally <sally@example.com>;, Bonzo <bonz@laugh.com>
Decoding to unicode is done automatically:
>>> m2 = message_from_string(str(m))
>>> m2['to']
'Éric <foo@example.com>'
When you parse a message, you can use the addresses
and groups
attributes of the header objects to access the groups and individual
addresses:
>>> m2['cc'].addresses
(Address(display_name='Bob', username='bob', domain='example.com'), Address(display_name='Sally', username='sally', domain='example.com'), Address(display_name='Bonzo', username='bonz', domain='laugh.com'))
>>> m2['cc'].groups
(Group(display_name='pals', addresses=(Address(display_name='Bob', username='bob', domain='example.com'), Address(display_name='Sally', username='sally', domain='example.com')), Group(display_name=None, addresses=(Address(display_name='Bonzo', username='bonz', domain='laugh.com'),))
In summary, if you use one of the new policies, header manipulation works the way it ought to: your application works with unicode strings, and the email package transparently encodes and decodes the unicode to and from the RFC standard Content Transfer Encodings.
Other API Changes¶
New BytesHeaderParser
, added to the parser
module to complement HeaderParser
and complete the Bytes
API.
New utility functions:
format_datetime()
: given adatetime
, produce a string formatted for use in an email header.parsedate_to_datetime()
: given a date string from an email header, convert it into an awaredatetime
, or a naivedatetime
if the offset is-0000
.localtime()
: With no argument, returns the current local time as an awaredatetime
using the localtimezone
. Given an awaredatetime
, converts it into an awaredatetime
using the localtimezone
.
ftplib¶
ftplib.FTP
now accepts asource_address
keyword argument to specify the(host, port)
to use as the source address in the bind call when creating the outgoing socket. (Contributed by Giampaolo Rodolà in bpo-8594.)The
FTP_TLS
class now provides a newccc()
function to revert control channel back to plaintext. This can be useful to take advantage of firewalls that know how to handle NAT with non-secure FTP without opening fixed ports. (Contributed by Giampaolo Rodolà in bpo-12139.)Added
ftplib.FTP.mlsd()
method which provides a parsable directory listing format and deprecatesftplib.FTP.nlst()
andftplib.FTP.dir()
. (Contributed by Giampaolo Rodolà in bpo-11072.)
functools¶
The functools.lru_cache()
decorator now accepts a typed
keyword
argument (that defaults to False
to ensure that it caches values of
different types that compare equal in separate cache slots. (Contributed
by Raymond Hettinger in bpo-13227.)
gc¶
It is now possible to register callbacks invoked by the garbage collector
before and after collection using the new callbacks
list.
hmac¶
A new compare_digest()
function has been added to prevent side
channel attacks on digests through timing analysis. (Contributed by Nick
Coghlan and Christian Heimes in bpo-15061.)
http¶
http.server.BaseHTTPRequestHandler
now buffers the headers and writes
them all at once when end_headers()
is
called. A new method flush_headers()
can be used to directly manage when the accumulated headers are sent.
(Contributed by Andrew Schaaf in bpo-3709.)
http.server
now produces valid HTML 4.01 strict
output.
(Contributed by Ezio Melotti in bpo-13295.)
http.client.HTTPResponse
now has a
readinto()
method, which means it can be used
as an io.RawIOBase
class. (Contributed by John Kuhn in
bpo-13464.)
html¶
html.parser.HTMLParser
is now able to parse broken markup without
raising errors, therefore the strict argument of the constructor and the
HTMLParseError
exception are now deprecated.
The ability to parse broken markup is the result of a number of bug fixes that
are also available on the latest bug fix releases of Python 2.7/3.2.
(Contributed by Ezio Melotti in bpo-15114, and bpo-14538,
bpo-13993, bpo-13960, bpo-13358, bpo-1745761,
bpo-755670, bpo-13357, bpo-12629, bpo-1200313,
bpo-670664, bpo-13273, bpo-12888, bpo-7311.)
A new html5
dictionary that maps HTML5 named character
references to the equivalent Unicode character(s) (e.g. html5['gt;'] ==
'>'
) has been added to the html.entities
module. The dictionary is
now also used by HTMLParser
. (Contributed by Ezio
Melotti in bpo-11113 and bpo-15156.)
imaplib¶
The IMAP4_SSL
constructor now accepts an SSLContext
parameter to control parameters of the secure channel.
(由 Sijin Joseph 在 bpo-8808 中贡献。)
inspect¶
A new getclosurevars()
function has been added. This function
reports the current binding of all names referenced from the function body and
where those names were resolved, making it easier to verify correct internal
state when testing code that relies on stateful closures.
(由 Meador Inge 和 Nick Coghlan 在 bpo-13062 中贡献。)
A new getgeneratorlocals()
function has been added. This
function reports the current binding of local variables in the generator's
stack frame, making it easier to verify correct internal state when testing
generators.
(由 Meador Inge 在 bpo-15153 中贡献。)
io¶
The open()
function has a new 'x'
mode that can be used to
exclusively create a new file, and raise a FileExistsError
if the file
already exists. It is based on the C11 'x' mode to fopen().
(由 David Townshend 在 bpo-12760 中贡献。)
The constructor of the TextIOWrapper
class has a new
write_through optional argument. If write_through is True
, calls to
write()
are guaranteed not to be buffered: any data
written on the TextIOWrapper
object is immediately handled to its
underlying binary buffer.
itertools¶
accumulate()
now takes an optional func
argument for
providing a user-supplied binary function.
logging¶
The basicConfig()
function now supports an optional handlers
argument taking an iterable of handlers to be added to the root logger.
A class level attribute append_nul
has
been added to SysLogHandler
to allow control of the
appending of the NUL
(\000
) byte to syslog records, since for some
daemons it is required while for others it is passed through to the log.
math¶
The math
module has a new function, log2()
, which returns
the base-2 logarithm of x.
(Written by Mark Dickinson in bpo-11888.)
mmap¶
The read()
method is now more compatible with other file-like
objects: if the argument is omitted or specified as None
, it returns the
bytes from the current file position to the end of the mapping. (Contributed
by Petri Lehtinen in bpo-12021.)
multiprocessing¶
The new multiprocessing.connection.wait()
function allows polling
multiple objects (such as connections, sockets and pipes) with a timeout.
(Contributed by Richard Oudkerk in bpo-12328.)
multiprocessing.Connection
objects can now be transferred over
multiprocessing connections.
(Contributed by Richard Oudkerk in bpo-4892.)
multiprocessing.Process
now accepts a daemon
keyword argument
to override the default behavior of inheriting the daemon
flag from
the parent process (bpo-6064).
New attribute multiprocessing.Process.sentinel
allows a
program to wait on multiple Process
objects at one
time using the appropriate OS primitives (for example, select
on
posix systems).
New methods multiprocessing.pool.Pool.starmap()
and
starmap_async()
provide
itertools.starmap()
equivalents to the existing
multiprocessing.pool.Pool.map()
and
map_async()
functions. (Contributed by Hynek
Schlawack in bpo-12708.)
nntplib¶
The nntplib.NNTP
class now supports the context management protocol to
unconditionally consume socket.error
exceptions and to close the NNTP
connection when done:
>>> from nntplib import NNTP
>>> with NNTP('news.gmane.org') as n:
... n.group('gmane.comp.python.committers')
...
('211 1755 1 1755 gmane.comp.python.committers', 1755, 1, 1755, 'gmane.comp.python.committers')
>>>
(由 Giampaolo Rodolà 在 bpo-9795 中贡献。)
os¶
The
os
module has a newpipe2()
function that makes it possible to create a pipe withO_CLOEXEC
orO_NONBLOCK
flags set atomically. This is especially useful to avoid race conditions in multi-threaded programs.The
os
module has a newsendfile()
function which provides an efficient "zero-copy" way for copying data from one file (or socket) descriptor to another. The phrase "zero-copy" refers to the fact that all of the copying of data between the two descriptors is done entirely by the kernel, with no copying of data into userspace buffers.sendfile()
can be used to efficiently copy data from a file on disk to a network socket, e.g. for downloading a file.(Patch submitted by Ross Lagerwall and Giampaolo Rodolà in bpo-10882.)
To avoid race conditions like symlink attacks and issues with temporary files and directories, it is more reliable (and also faster) to manipulate file descriptors instead of file names. Python 3.3 enhances existing functions and introduces new functions to work on file descriptors (bpo-4761, bpo-10755 and bpo-14626).
The
os
module has a newfwalk()
function similar towalk()
except that it also yields file descriptors referring to the directories visited. This is especially useful to avoid symlink races.The following functions get new optional dir_fd (paths relative to directory descriptors) and/or follow_symlinks (not following symlinks):
access()
,chflags()
,chmod()
,chown()
,link()
,lstat()
,mkdir()
,mkfifo()
,mknod()
,open()
,readlink()
,remove()
,rename()
,replace()
,rmdir()
,stat()
,symlink()
,unlink()
,utime()
. Platform support for using these parameters can be checked via the setsos.supports_dir_fd
andos.supports_follows_symlinks
.The following functions now support a file descriptor for their path argument:
chdir()
,chmod()
,chown()
,execve()
,listdir()
,pathconf()
,exists()
,stat()
,statvfs()
,utime()
. Platform support for this can be checked via theos.supports_fd
set.
access()
accepts aneffective_ids
keyword argument to turn on using the effective uid/gid rather than the real uid/gid in the access check. Platform support for this can be checked via thesupports_effective_ids
set.The
os
module has two new functions:getpriority()
andsetpriority()
. They can be used to get or set process niceness/priority in a fashion similar toos.nice()
but extended to all processes instead of just the current one.(Patch submitted by Giampaolo Rodolà in bpo-10784.)
The new
os.replace()
function allows cross-platform renaming of a file with overwriting the destination. Withos.rename()
, an existing destination file is overwritten under POSIX, but raises an error under Windows. (Contributed by Antoine Pitrou in bpo-8828.)The stat family of functions (
stat()
,fstat()
, andlstat()
) now support reading a file's timestamps with nanosecond precision. Symmetrically,utime()
can now write file timestamps with nanosecond precision. (Contributed by Larry Hastings in bpo-14127.)The new
os.get_terminal_size()
function queries the size of the terminal attached to a file descriptor. See alsoshutil.get_terminal_size()
. (Contributed by Zbigniew Jędrzejewski-Szmek in bpo-13609.)
New functions to support Linux extended attributes (bpo-12720):
getxattr()
,listxattr()
,removexattr()
,setxattr()
.New interface to the scheduler. These functions control how a process is allocated CPU time by the operating system. New functions:
sched_get_priority_max()
,sched_get_priority_min()
,sched_getaffinity()
,sched_getparam()
,sched_getscheduler()
,sched_rr_get_interval()
,sched_setaffinity()
,sched_setparam()
,sched_setscheduler()
,sched_yield()
,New functions to control the file system:
posix_fadvise()
: Announces an intention to access data in a specific pattern thus allowing the kernel to make optimizations.posix_fallocate()
: Ensures that enough disk space is allocated for a file.sync()
: Force write of everything to disk.
Additional new posix functions:
lockf()
: Apply, test or remove a POSIX lock on an open file descriptor.pread()
: Read from a file descriptor at an offset, the file offset remains unchanged.pwrite()
: Write to a file descriptor from an offset, leaving the file offset unchanged.readv()
: Read from a file descriptor into a number of writable buffers.truncate()
: Truncate the file corresponding to path, so that it is at most length bytes in size.waitid()
: Wait for the completion of one or more child processes.writev()
: Write the contents of buffers to a file descriptor, where buffers is an arbitrary sequence of buffers.getgrouplist()
(bpo-9344): Return list of group ids that specified user belongs to.
times()
anduname()
: Return type changed from a tuple to a tuple-like object with named attributes.Some platforms now support additional constants for the
lseek()
function, such asos.SEEK_HOLE
andos.SEEK_DATA
.New constants
RTLD_LAZY
,RTLD_NOW
,RTLD_GLOBAL
,RTLD_LOCAL
,RTLD_NODELETE
,RTLD_NOLOAD
, andRTLD_DEEPBIND
are available on platforms that support them. These are for use with thesys.setdlopenflags()
function, and supersede the similar constants defined inctypes
andDLFCN
. (Contributed by Victor Stinner in bpo-13226.)os.symlink()
now accepts (and ignores) thetarget_is_directory
keyword argument on non-Windows platforms, to ease cross-platform support.
pdb¶
Tab-completion is now available not only for command names, but also their
arguments. For example, for the break
command, function and file names
are completed.
(由 Georg Brandl 在 bpo-14210 中贡献)
pickle¶
pickle.Pickler
objects now have an optional
dispatch_table
attribute allowing per-pickler
reduction functions to be set.
(由 Richard Oudkerk 在 bpo-14166 中贡献。)
pydoc¶
The Tk GUI and the serve()
function have been removed from the
pydoc
module: pydoc -g
and serve()
have been deprecated
in Python 3.2.
re¶
str
regular expressions now support \u
and \U
escapes.
(由 Serhiy Storchaka 在 bpo-3665 中贡献。)
sched¶
run()
now accepts a blocking parameter which when set to false makes the method execute the scheduled events due to expire soonest (if any) and then return immediately. This is useful in case you want to use thescheduler
in non-blocking applications. (Contributed by Giampaolo Rodolà in bpo-13449.)scheduler
class can now be safely used in multi-threaded environments. (Contributed by Josiah Carlson and Giampaolo Rodolà in bpo-8684.)timefunc and delayfunct parameters of
scheduler
class constructor are now optional and defaults totime.time()
andtime.sleep()
respectively. (Contributed by Chris Clark in bpo-13245.)enter()
andenterabs()
argument parameter is now optional. (Contributed by Chris Clark in bpo-13245.)enter()
andenterabs()
now accept a kwargs parameter. (Contributed by Chris Clark in bpo-13245.)
select¶
Solaris and derivative platforms have a new class select.devpoll
for high performance asynchronous sockets via /dev/poll
.
(Contributed by Jesús Cea Avión in bpo-6397.)
shlex¶
The previously undocumented helper function quote
from the
pipes
modules has been moved to the shlex
module and
documented. quote()
properly escapes all characters in a string
that might be otherwise given special meaning by the shell.
shutil¶
新的函数:
disk_usage()
: provides total, used and free disk space statistics. (Contributed by Giampaolo Rodolà in bpo-12442.)chown()
: allows one to change user and/or group of the given path also specifying the user/group names and not only their numeric ids. (Contributed by Sandro Tosi in bpo-12191.)shutil.get_terminal_size()
: returns the size of the terminal window to which the interpreter is attached. (Contributed by Zbigniew Jędrzejewski-Szmek in bpo-13609.)
copy2()
andcopystat()
now preserve file timestamps with nanosecond precision on platforms that support it. They also preserve file "extended attributes" on Linux. (Contributed by Larry Hastings in bpo-14127 and bpo-15238.)Several functions now take an optional
symlinks
argument: when that parameter is true, symlinks aren't dereferenced and the operation instead acts on the symlink itself (or creates one, if relevant). (Contributed by Hynek Schlawack in bpo-12715.)When copying files to a different file system,
move()
now handles symlinks the way the posixmv
command does, recreating the symlink rather than copying the target file contents. (Contributed by Jonathan Niehof in bpo-9993.)move()
now also returns thedst
argument as its result.rmtree()
is now resistant to symlink attacks on platforms which support the newdir_fd
parameter inos.open()
andos.unlink()
. (Contributed by Martin von Löwis and Hynek Schlawack in bpo-4489.)
signal¶
signal
模块新增的函数:pthread_sigmask()
: 获取和/或改变调用方线程的信号掩码(由 Jean-Paul Calderone 在 bpo-8407 中贡献);pthread_kill()
: 向指定线程发送信号;sigpending()
: 检查挂起的函数;sigwait()
: 等待一个信号;sigwaitinfo()
: 等待信号,返回相关的详细信息;sigtimedwait()
: likesigwaitinfo()
but with a timeout.
The signal handler writes the signal number as a single byte instead of a nul byte into the wakeup file descriptor. So it is possible to wait more than one signal and know which signals were raised.
signal.signal()
andsignal.siginterrupt()
raise an OSError, instead of a RuntimeError: OSError has an errno attribute.
smtpd¶
The smtpd
module now supports RFC 5321 (extended SMTP) and RFC 1870
(size extension). Per the standard, these extensions are enabled if and only
if the client initiates the session with an EHLO
command.
(Initial ELHO
support by Alberto Trevino. Size extension by Juhana
Jauhiainen. Substantial additional work on the patch contributed by Michele
Orrù and Dan Boswell. bpo-8739)
smtplib¶
The SMTP
, SMTP_SSL
, and
LMTP
classes now accept a source_address
keyword argument
to specify the (host, port)
to use as the source address in the bind call
when creating the outgoing socket. (Contributed by Paulo Scardine in
bpo-11281.)
SMTP
now supports the context management protocol, allowing an
SMTP
instance to be used in a with
statement. (Contributed
by Giampaolo Rodolà in bpo-11289.)
The SMTP_SSL
constructor and the starttls()
method now accept an SSLContext parameter to control parameters of the secure
channel. (Contributed by Kasun Herath in bpo-8809.)
socket¶
The
socket
class now exposes additional methods to process ancillary data when supported by the underlying platform:(Contributed by David Watson in bpo-6560, based on an earlier patch by Heiko Wundram)
The
socket
class now supports the PF_CAN protocol family (https://en.wikipedia.org/wiki/Socketcan), on Linux (https://lwn.net/Articles/253425).(Contributed by Matthias Fuchs, updated by Tiago Gonçalves in bpo-10141.)
The
socket
class now supports the PF_RDS protocol family (https://en.wikipedia.org/wiki/Reliable_Datagram_Sockets and https://oss.oracle.com/projects/rds).The
socket
class now supports thePF_SYSTEM
protocol family on OS X. (Contributed by Michael Goderbauer in bpo-13777.)New function
sethostname()
allows the hostname to be set on Unix systems if the calling process has sufficient privileges. (Contributed by Ross Lagerwall in bpo-10866.)
socketserver¶
BaseServer
now has an overridable method
service_actions()
that is called by the
serve_forever()
method in the service loop.
ForkingMixIn
now uses this to clean up zombie
child processes. (Contributed by Justin Warkentin in bpo-11109.)
sqlite3¶
New sqlite3.Connection
method
set_trace_callback()
can be used to capture a trace of
all sql commands processed by sqlite. (Contributed by Torsten Landschoff
in bpo-11688.)
ssl¶
The
ssl
module has two new random generation functions:RAND_bytes()
: generate cryptographically strong pseudo-random bytes.RAND_pseudo_bytes()
: 生成伪随机字节。
(由 Victor Stinner 在 bpo-12049 中贡献。)
The
ssl
module now exposes a finer-grained exception hierarchy in order to make it easier to inspect the various kinds of errors. (Contributed by Antoine Pitrou in bpo-11183.)load_cert_chain()
now accepts a password argument to be used if the private key is encrypted. (Contributed by Adam Simpkins in bpo-12803.)Diffie-Hellman key exchange, both regular and Elliptic Curve-based, is now supported through the
load_dh_params()
andset_ecdh_curve()
methods. (Contributed by Antoine Pitrou in bpo-13626 and bpo-13627.)SSL sockets have a new
get_channel_binding()
method allowing the implementation of certain authentication mechanisms such as SCRAM-SHA-1-PLUS. (Contributed by Jacek Konieczny in bpo-12551.)You can query the SSL compression algorithm used by an SSL socket, thanks to its new
compression()
method. The new attributeOP_NO_COMPRESSION
can be used to disable compression. (Contributed by Antoine Pitrou in bpo-13634.)Support has been added for the Next Protocol Negotiation extension using the
ssl.SSLContext.set_npn_protocols()
method. (Contributed by Colin Marc in bpo-14204.)SSL errors can now be introspected more easily thanks to
library
andreason
attributes. (Contributed by Antoine Pitrou in bpo-14837.)The
get_server_certificate()
function now supports IPv6. (Contributed by Charles-François Natali in bpo-11811.)New attribute
OP_CIPHER_SERVER_PREFERENCE
allows setting SSLv3 server sockets to use the server's cipher ordering preference rather than the client's (bpo-13635).
stat¶
The undocumented tarfile.filemode function has been moved to
stat.filemode()
. It can be used to convert a file's mode to a string of
the form '-rwxrwxrwx'.
(由 Giampaolo Rodolà 在 bpo-14807 中贡献。)
struct¶
The struct
module now supports ssize_t
and size_t
via the
new codes n
and N
, respectively. (Contributed by Antoine Pitrou
in bpo-3163.)
subprocess¶
Command strings can now be bytes objects on posix platforms. (Contributed by Victor Stinner in bpo-8513.)
A new constant DEVNULL
allows suppressing output in a
platform-independent fashion. (Contributed by Ross Lagerwall in
bpo-5870.)
sys¶
The sys
module has a new thread_info
named
tuple holding information about the thread implementation
(bpo-11223).
tarfile¶
tarfile
now supports lzma
encoding via the lzma
module.
(Contributed by Lars Gustäbel in bpo-5689.)
tempfile¶
tempfile.SpooledTemporaryFile
's
truncate()
method now accepts
a size
parameter. (Contributed by Ryan Kelly in bpo-9957.)
textwrap¶
The textwrap
module has a new indent()
that makes
it straightforward to add a common prefix to selected lines in a block
of text (bpo-13857).
threading¶
threading.Condition
, threading.Semaphore
,
threading.BoundedSemaphore
, threading.Event
, and
threading.Timer
, all of which used to be factory functions returning a
class instance, are now classes and may be subclassed. (Contributed by Éric
Araujo in bpo-10968.)
The threading.Thread
constructor now accepts a daemon
keyword
argument to override the default behavior of inheriting the daemon
flag
value from the parent thread (bpo-6064).
The formerly private function _thread.get_ident
is now available as the
public function threading.get_ident()
. This eliminates several cases of
direct access to the _thread
module in the stdlib. Third party code that
used _thread.get_ident
should likewise be changed to use the new public
interface.
time¶
The PEP 418 added new functions to the time
module:
get_clock_info()
: Get information on a clock.monotonic()
: Monotonic clock (cannot go backward), not affected by system clock updates.perf_counter()
: Performance counter with the highest available resolution to measure a short duration.process_time()
: Sum of the system and user CPU time of the current process.
Other new functions:
clock_getres()
,clock_gettime()
andclock_settime()
functions withCLOCK_xxx
constants. (Contributed by Victor Stinner in bpo-10278.)
To improve cross platform consistency, sleep()
now raises a
ValueError
when passed a negative sleep value. Previously this was an
error on posix, but produced an infinite sleep on Windows.
types¶
Add a new types.MappingProxyType
class: Read-only proxy of a mapping.
(bpo-14386)
The new functions types.new_class()
and types.prepare_class()
provide support
for PEP 3115 compliant dynamic type creation. (bpo-14588)
unittest¶
assertRaises()
, assertRaisesRegex()
, assertWarns()
, and
assertWarnsRegex()
now accept a keyword argument msg when used as
context managers. (Contributed by Ezio Melotti and Winston Ewert in
bpo-10775.)
unittest.TestCase.run()
now returns the TestResult
object.
urllib¶
The Request
class, now accepts a method argument
used by get_method()
to determine what HTTP method
should be used. For example, this will send a 'HEAD'
request:
>>> urlopen(Request('https://www.python.org', method='HEAD'))
webbrowser¶
The webbrowser
module supports more "browsers": Google Chrome (named
chrome, chromium, chrome-browser or
chromium-browser depending on the version and operating system),
and the generic launchers xdg-open, from the FreeDesktop.org
project, and gvfs-open, which is the default URI handler for GNOME
3. (The former contributed by Arnaud Calmettes in bpo-13620, the latter
by Matthias Klose in bpo-14493.)
xml.etree.ElementTree¶
The xml.etree.ElementTree
module now imports its C accelerator by
default; there is no longer a need to explicitly import
xml.etree.cElementTree
(this module stays for backwards compatibility,
but is now deprecated). In addition, the iter
family of methods of
Element
has been optimized (rewritten in C).
The module's documentation has also been greatly improved with added examples
and a more detailed reference.
zlib¶
New attribute zlib.Decompress.eof
makes it possible to distinguish
between a properly formed compressed stream and an incomplete or truncated one.
(Contributed by Nadeem Vawda in bpo-12646.)
New attribute zlib.ZLIB_RUNTIME_VERSION
reports the version string of
the underlying zlib
library that is loaded at runtime. (Contributed by
Torsten Landschoff in bpo-12306.)
性能优化¶
已增加的主要性能改善:
得益于:pep:393 ,Unicode 字符串的某些操作已得到优化:
the memory footprint is divided by 2 to 4 depending on the text
将 ASCII 字符串编码为 UTF-8 不再需要对字符进行编码,UTF-8 的表示法与 ASCII 的表示法是共享的
the UTF-8 encoder has been optimized
repeating a single ASCII letter and getting a substring of an ASCII string is 4 times faster
UTF-8 编码现在快 2 到 4 倍。 UTF-16 编码的速度现在提高了 10 倍。
(由 Serhiy Storchaka 在 bpo-14624, bpo-14738 和 bpo-15026 中贡献)。
构建和 C API 的改变¶
针对 Python 构建过程和 C API 的改变包括:
新的 PEP 3118 相关功能:
PEP 393 添加了新的 Unicode 类型,宏和函数
高阶 API
低阶 API:
PyUnicode_DATA
,PyUnicode_1BYTE_DATA
,PyUnicode_2BYTE_DATA
,PyUnicode_4BYTE_DATA
PyUnicode_KIND
withPyUnicode_Kind
enum:PyUnicode_WCHAR_KIND
,PyUnicode_1BYTE_KIND
,PyUnicode_2BYTE_KIND
,PyUnicode_4BYTE_KIND
PyArg_ParseTuple
现在接受c
格式的bytearray
(bpo-12380)。
弃用¶
不支持的操作系统¶
由于缺少维护人员,不再支持 OS/2 和 VMS 系统 。
由于维护负担,将 COMSPEC
设置为 command.com
的 Windows平台(含Windows 2000)不再受支持。
OSF支持在3.2中被弃用,现在已经被完全删除。
已弃用的 Python 模块、函数和方法¶
向
object.__format__()
传递非空字符串的做法已被弃用,在 Python 3.4 中会产生一个TypeError
(bpo-9856)。由于:pep:393,
unicode_internal
编解码器已被弃用 。请使用 UTF-8、UTF-16 (utf-16-le
或``utf-16-be``) 或 UTF-32 (utf-32-le
或``utf-32-be``)ftplib.FTP.nlst()
andftplib.FTP.dir()
: useftplib.FTP.mlsd()
platform.popen()
: use thesubprocess
module. Check especially the 使用 subprocess 模块替换旧函数 section (bpo-11377).bpo-13374: The Windows bytes API has been deprecated in the
os
module. Use Unicode filenames, instead of bytes filenames, to not depend on the ANSI code page anymore and to support any filename.bpo-13988: The
xml.etree.cElementTree
module is deprecated. The accelerator is used automatically whenever available.The behaviour of
time.clock()
depends on the platform: use the newtime.perf_counter()
ortime.process_time()
function instead, depending on your requirements, to have a well defined behaviour.The
os.stat_float_times()
function is deprecated.abc
module:abc.abstractproperty
has been deprecated, useproperty
withabc.abstractmethod()
instead.abc.abstractclassmethod
has been deprecated, useclassmethod
withabc.abstractmethod()
instead.abc.abstractstaticmethod
has been deprecated, usestaticmethod
withabc.abstractmethod()
instead.
importlib
package:importlib.abc.SourceLoader.path_mtime()
is now deprecated in favour ofimportlib.abc.SourceLoader.path_stats()
as bytecode files now store both the modification time and size of the source file the bytecode file was compiled from.
已弃用的 C API 函数和类型¶
Py_UNICODE
已经在 PEP 393 弃用,并将于 Python 4 中移除。所有使用此类型的函数都已弃用:
Unicode functions and methods using Py_UNICODE
and
Py_UNICODE* types:
PyUnicode_FromUnicode
: usePyUnicode_FromWideChar()
orPyUnicode_FromKindAndData()
PyUnicode_AS_UNICODE
,PyUnicode_AsUnicode()
,PyUnicode_AsUnicodeAndSize()
: usePyUnicode_AsWideCharString()
PyUnicode_AS_DATA
: usePyUnicode_DATA
withPyUnicode_READ
andPyUnicode_WRITE
PyUnicode_GET_SIZE
,PyUnicode_GetSize()
: usePyUnicode_GET_LENGTH
orPyUnicode_GetLength()
PyUnicode_GET_DATA_SIZE
: usePyUnicode_GET_LENGTH(str) * PyUnicode_KIND(str)
(only work on ready strings)PyUnicode_AsUnicodeCopy()
: usePyUnicode_AsUCS4Copy()
orPyUnicode_AsWideCharString()
PyUnicode_GetMax()
Functions and macros manipulating Py_UNICODE* strings:
Py_UNICODE_strlen()
: usePyUnicode_GetLength()
orPyUnicode_GET_LENGTH
Py_UNICODE_strcat()
: usePyUnicode_CopyCharacters()
orPyUnicode_FromFormat()
Py_UNICODE_strcpy()
,Py_UNICODE_strncpy()
,Py_UNICODE_COPY()
: usePyUnicode_CopyCharacters()
orPyUnicode_Substring()
Py_UNICODE_strcmp()
: usePyUnicode_Compare()
Py_UNICODE_strncmp()
: usePyUnicode_Tailmatch()
Py_UNICODE_strchr()
,Py_UNICODE_strrchr()
: usePyUnicode_FindChar()
Py_UNICODE_FILL()
: usePyUnicode_Fill()
Py_UNICODE_MATCH
编码器:
PyUnicode_Encode()
: usePyUnicode_AsEncodedObject()
PyUnicode_EncodeUTF7()
PyUnicode_EncodeUTF8()
: usePyUnicode_AsUTF8()
orPyUnicode_AsUTF8String()
PyUnicode_EncodeUTF32()
PyUnicode_EncodeUTF16()
PyUnicode_EncodeUnicodeEscape()
usePyUnicode_AsUnicodeEscapeString()
PyUnicode_EncodeRawUnicodeEscape()
usePyUnicode_AsRawUnicodeEscapeString()
PyUnicode_EncodeLatin1()
: usePyUnicode_AsLatin1String()
PyUnicode_EncodeASCII()
: usePyUnicode_AsASCIIString()
PyUnicode_EncodeCharmap()
PyUnicode_TranslateCharmap()
PyUnicode_EncodeMBCS()
: usePyUnicode_AsMBCSString()
orPyUnicode_EncodeCodePage()
(withCP_ACP
code_page)PyUnicode_EncodeDecimal()
,PyUnicode_TransformDecimalToASCII()
弃用的功能¶
array
模块的``'u'`` 格式代码现已弃用,将在 Python 4 中与 (Py_UNICODE
) API 的其他部分一起删除。
移植到 Python 3.3¶
本节列出了先前描述的更改以及可能需要更改代码的其他错误修正.
移植 Python 代码¶
默认启用哈希随机化。 将
PYTHONHASHSEED
环境变量设为0
可禁用哈希随机化。 另请参阅object.__hash__()
方法。bpo-12326: 在 Linux 上,sys.platform 不再包含主要版本。现在它始终是 "linux",而不是 "linux2" 或 "linux3",这取决于用于构建 Python 的 Linux 版本。请用 sys.platform.startswith('linux') 替换 sys.platform == 'linux2',如果不需要支持较旧的 Python 版本,则可直接替换成 sys.platform == 'linux'。
bpo-13847, bpo-14180:
time
和datetime
: 现在如果时间戳超出范围将会引发OverflowError
而不是ValueError
。 现在如果 C 函数gmtime()
或localtime()
失败 将会引发OSError
。The default finders used by import now utilize a cache of what is contained within a specific directory. If you create a Python source file or sourceless bytecode file, make sure to call
importlib.invalidate_caches()
to clear out the cache for the finders to notice the new file.ImportError
now uses the full name of the module that was attempted to be imported. Doctests that check ImportErrors' message will need to be updated to use the full name of the module instead of just the tail of the name.The index argument to
__import__()
now defaults to 0 instead of -1 and no longer support negative values. It was an oversight when PEP 328 was implemented that the default value remained -1. If you need to continue to perform a relative import followed by an absolute import, then perform the relative import using an index of 1, followed by another import using an index of 0. It is preferred, though, that you useimportlib.import_module()
rather than call__import__()
directly.__import__()
no longer allows one to use an index value other than 0 for top-level modules. E.g.__import__('sys', level=1)
is now an error.Because
sys.meta_path
andsys.path_hooks
now have finders on them by default, you will most likely want to uselist.insert()
instead oflist.append()
to add to those lists.Because
None
is now inserted intosys.path_importer_cache
, if you are clearing out entries in the dictionary of paths that do not have a finder, you will need to remove keys paired with values ofNone
andimp.NullImporter
to be backwards-compatible. This will lead to extra overhead on older versions of Python that re-insertNone
intosys.path_importer_cache
where it represents the use of implicit finders, but semantically it should not change anything.importlib.abc.Finder
no longer specifies afind_module()
abstract method that must be implemented. If you were relying on subclasses to implement that method, make sure to check for the method's existence first. You will probably want to check forfind_loader()
first, though, in the case of working with path entry finders.pkgutil
has been converted to useimportlib
internally. This eliminates many edge cases where the old behaviour of the PEP 302 import emulation failed to match the behaviour of the real import system. The import emulation itself is still present, but is now deprecated. Thepkgutil.iter_importers()
andpkgutil.walk_packages()
functions special case the standard import hooks so they are still supported even though they do not provide the non-standarditer_modules()
method.A longstanding RFC-compliance bug (bpo-1079) in the parsing done by
email.header.decode_header()
has been fixed. Code that uses the standard idiom to convert encoded headers into unicode (str(make_header(decode_header(h))
) will see no change, but code that looks at the individual tuples returned by decode_header will see that whitespace that precedes or followsASCII
sections is now included in theASCII
section. Code that builds headers usingmake_header
should also continue to work without change, sincemake_header
continues to add whitespace betweenASCII
and non-ASCII
sections if it is not already present in the input strings.email.utils.formataddr()
now does the correct content transfer encoding when passed non-ASCII
display names. Any code that depended on the previous buggy behavior that preserved the non-ASCII
unicode in the formatted output string will need to be changed (bpo-1690608).poplib.POP3.quit()
may now raise protocol errors like all otherpoplib
methods. Code that assumesquit
does not raisepoplib.error_proto
errors may need to be changed if errors onquit
are encountered by a particular application (bpo-11291).The
strict
argument toemail.parser.Parser
, deprecated since Python 2.4, has finally been removed.The deprecated method
unittest.TestCase.assertSameElements
has been removed.The deprecated variable
time.accept2dyear
has been removed.被弃用的
Context._clamp
属性已从decimal
模块中移除。 在此之前它已被公有属性clamp
取代。 (参见 bpo-8540。)The undocumented internal helper class
SSLFakeFile
has been removed fromsmtplib
, since its functionality has long been provided directly bysocket.socket.makefile()
.Passing a negative value to
time.sleep()
on Windows now raises an error instead of sleeping forever. It has always raised an error on posix.The
ast.__version__
constant has been removed. If you need to make decisions affected by the AST version, usesys.version_info
to make the decision.Code that used to work around the fact that the
threading
module used factory functions by subclassing the private classes will need to change to subclass the now-public classes.The undocumented debugging machinery in the threading module has been removed, simplifying the code. This should have no effect on production code, but is mentioned here in case any application debug frameworks were interacting with it (bpo-13550).
移植 C 代码¶
In the course of changes to the buffer API the undocumented
smalltable
member of thePy_buffer
structure has been removed and the layout of thePyMemoryViewObject
has changed.All extensions relying on the relevant parts in
memoryobject.h
orobject.h
must be rebuilt.Due to PEP 393, the
Py_UNICODE
type and all functions using this type are deprecated (but will stay available for at least five years). If you were using low-level Unicode APIs to construct and access unicode objects and you want to benefit of the memory footprint reduction provided by PEP 393, you have to convert your code to the new Unicode API.However, if you only have been using high-level functions such as
PyUnicode_Concat()
,PyUnicode_Join()
orPyUnicode_FromFormat()
, your code will automatically take advantage of the new unicode representations.PyImport_GetMagicNumber()
now returns-1
upon failure.As a negative value for the level argument to
__import__()
is no longer valid, the same now holds forPyImport_ImportModuleLevel()
. This also means that the value of level used byPyImport_ImportModuleEx()
is now0
instead of-1
.
Building C extensions¶
The range of possible file names for C extensions has been narrowed. Very rarely used spellings have been suppressed: under POSIX, files named
xxxmodule.so
,xxxmodule.abi3.so
andxxxmodule.cpython-*.so
are no longer recognized as implementing thexxx
module. If you had been generating such files, you have to switch to the other spellings (i.e., remove themodule
string from the file names).(在 bpo-14040 中实现。)